Belly buttons

For kids:  You got your belly button when God took you out of the oven and gave a little poke with his finger to see if you were done.

For grownups:   The belly button proves we are on a continuous living thread joined to every one of our ancestors.  Our life drawn in four dimensions has a tiny spot where it is joined to another's with a gossamer-thin thread. That thread goes to both parents and all their forebears.

The images help visualize a 4-D life map.
I can think one but I've never seen one.